ONE OF Irish actress Saoirse Ronan’s first screen roles, she was nominated for a Best Supporting Actress Oscar in the 2007 adaptation of Ian McEwan’s bestselling novel, “Atonement.” She was 13 at the time.

With “On Chesil Beach,” Ronan is in yet another adaptation of a McEwan book, this time in one of the principal roles. The novella, which was short-listed for the prestigious Man Booker Prize, is a love story set in 1962 England. Ronan plays Florence Ponting, a young upper middle-class violinist in a string quartet. She meets and soon falls in love with Edward Mayhew (Billy Howle), a gifted graduate student who comes from a troubled, and more working class background.

They marry and go to Chesil Beach, a resort on the Dorset coast, for their honeymoon. But on their wedding night, their fairytale romance goes terribly wrong. After awkward attempts to consummate their marriage, and both confessing to their virginity, Florence runs off in revulsion. Brief flashbacks suggest the reason for Florence’s horror at Edward’s understandable clumsiness, but she never tells him about her past.

Florence Ponting, a young upper middle-class violinist in a string quartet.

Instead, when he runs after her, she suggests they have a sexless marriage and gives her permission for him to take lovers. Edward, insulted and offended, not only rejects Florence’s proposal, but walks away from her and their union. The story jumps ahead ten years, and finally into the 21st century, as we gets hints of how Florence and Edward’s lives play out, setting the audience up for its sentimental and contrived conclusion.

McEwan wrote the screenplay, but changed his original story to include the seemingly pasted-on ending. Pressure from producers perhaps forced his hand, as there is a ham-handedness to it that betrays the rest of this very fine, beautifully and sensitively acted film. Its impressive supporting cast includes Emily Watson, Sam West, Adrian Scarborough and Anne-Marie Duff.

Extras include several deleted scenes and the featurette, containing interviews with cast members, the director, writer and a producer. McEwan says the story of “On Chesil Beach” is “about the ways in which we’re not only products of our specific genetic makeup – what we were born with – but we’re also creatures of our time. This was a time when it was very difficult to talk about sex or to acknowledge difficulties.”

Director Dominic Cooke describes Florence’s character as “very talented” and wanting to “give up the repressive environment” of her cold parents. Ronan explains that music had become Florence’s way of dealing with trauma she “suffered early in her life.” McEwan notes that Florence and Edward “deeply fulfill each other’s need to start explaining their pasts … They find in each other a willing listener … but their emotional understanding is running ahead of their physical understanding.”

Ronan agrees. “They’re the savior for one another.” Cooke says he wanted to illustrate a “feeling of something coming in the air … the spirit of release of the ’60s.”

McEwan praises Ronan’s acting talent: “She has a gift of remarkable inwardness … just in the way she listens.” One of his challenges in writing the screenplay, he says, is that he realized everyone who had read the book had his or her own version of it already. Ronan notes that McEwan “seems to appreciate how a moment can change everything.” Adds the author, “… and how doing nothing can completely change your entire future.”